In the past, the off-angle (that is, the tilt angle) of a (100) plane substrate in the manufacture of silicon epitaxial wafers has been specified in SEMI (Semiconductor Equipment and Materials International) standards to be no more than 2° (SEMI M2-87).
More recently, substrates with a tilt angle of 1° or less have come into mainstream use through increases in substrate machining precision.
For example, Japanese Patent Publication H3-61634 discloses a technique aimed at reducing microscopic defects (teardrops) during epitaxial growth, in which the angle θ in the [011] direction or [011] direction or the angle θ in the [011] direction or [011] direction with respect to the [100] axis was 5′≦θ≦2° and φ≦10′, or 5′≦φ≦2° and θ≦10′.
The underlines of the numbers indicating direction refer to the lines that ordinarily go over the numbers in crystallographic notation, but underlines will be used herein for the sake of convenience.
However, when a silicon (100) substrate wafer was epitaxially grown within these numerical ranges, the epitaxial wafer surface was sometimes rougher than the substrate wafer surface, which made it difficult to control the micro-roughness of the epitaxial wafer surface.
In view of this, Japanese Patent 3,081,706 discloses a method for improving the above-mentioned micro-roughness, in which the above-mentioned angle ranges for the slicing orientation are specified to be 30′≦θ≦2° and 30′≦φ≦2°.